Anniversary of the Columbia Accident - January 16, 2003

On Sun, 16 Jan 2005 21:44:44 -0600, Pat Flannery wrote:



OM wrote:

On Sun, 16 Jan 2005 22:42:43 GMT, Fred J. McCall
wrote:



Uh, graphite IS carbon....



...True, but probably less accurate than just using carbon fiber
instead of graphite.



Yeah- but "charcoal"? You're going to reenter the atmosphere with wing
leading edges made out of a combustible substance?



Right, it is combustible, that's why it's coated with a very thin layer of
silicon carbide (SiC), which isn't combustible. Remove the thin layer of
SiC and the leading edge burns.

Craig Fink

Craig Fink wrote:

Right, it is combustible, that's why it's coated with a very thin layer of
silicon carbide (SiC), which isn't combustible. Remove the thin layer of
SiC and the leading edge burns.



There may be some problem here in regards to what terminology we are
using- graphite is pure carbon and is what the Germans used to make the
V-2 exhaust vanes out of.
Charcoal, at least in the United States, is wood that has been heated to
the point of chemical breakdown in a very low oxygen environment, and is
then formed into briquettes that are used as easily combusted,
clean-burning coals during cooking. This is not what you want to make a
leading edge heatshield out of unless you want to cook steaks over the
still burning leading edge of the Shuttle's wing after it lands, and
watch that leading edge slowly transform into light gray ash.

Pat

On Sun, 16 Jan 2005 22:42:43 +0000, Fred J. McCall wrote:

Craig Fink wrote:

:On Sun, 16 Jan 2005 12:11:39 -0600, Pat Flannery wrote:
:
: Craig Fink wrote:
:
:The Reinforced Carbon Carbon (RCC) leading edge is essentially a high
:strength charcoal that can withstand the extreme temperatures of entry.
:
: Wouldn't "graphite" be a better discription? The only winged spacecraft
: I can think of that had a charcoal leading edge during reentry was that
: second German A4b with the wooden wings.
:
:I would think more like a composite. The graphite is the high strength
art, but the graphite fibers are glued together with carbon (essentially
:charcoal). Kind of like fiberglass/epoxy composite, except instead of
:fiber glass it has fiber graphite, and instead of epoxy it has carbon to
:hold it all together.

Uh, graphite IS carbon....

Diamond would be better....

Craig Fink wrote:

Diamond would be better....



I'm sure it would withstand foam impacts quite well. :-)
The main Pioneer Venus entry probe had a window for one of its sensors
cut out of a natural diamond, and eight other windows cut from man-made
sapphire- a flying jewelry store!

Pat

On Mon, 17 Jan 2005 14:14:04 -0600, Pat Flannery wrote:



Craig Fink wrote:

Diamond would be better....



I'm sure it would withstand foam impacts quite well. :-)

If you can't make a diamond as big as the Shuttles heat shield, your going
to have to use many diamonds. Then your going to have to find something to
put them together with. How about we epoxy them together the use the
process you described earlier to turn the epoxy into charcoal. BTW, charcoal
can be made of many different things, wood, coal, natural gas, epoxy, even
a tortilla.

So, is your new heatshield as strong as diamond or as weak as charcoal?
Probably somewhere inbetween.

Craig Fink

On Mon, 17 Jan 2005 14:14:04 -0600, Pat Flannery
wrote:

I'm sure it would withstand foam impacts quite well. :-)
The main Pioneer Venus entry probe had a window for one of its sensors
cut out of a natural diamond, and eight other windows cut from man-made
sapphire- a flying jewelry store!

Yeah, I know I'm really far behind here, but it's a good story.

NASA had to fill out a form promising to export the diamond, because
otherwise the subcontractor who had imported the diamond would have
had to pay some immense duty on it. Apparently, this was pretty
unusual and everyone got really excited about it. The sub couldn't
sign, because they weren't going to do the actual exporting; the
contractor ditto; so NASA had to do it. So the request had to go up
the chain and the signed paperwork went down it, and Treasury was
happy.

Dropping it into the Atlantic counts as exporting it, incidentally, as
long as it's beyond the twelve-mile limit. Or maybe the
two-hundred-mile economic zone limit.

Mary

--
Mary Shafer Retired aerospace research engineer